Triglyceride transport from the circulation into tissues depends upon prior hydrolysis of lipoprotein-bound triglyceride by lipoprotein lipase. Our research will be focused on factors regulating the activity of this enzyme. A comparison of amino acid composition, peptide mapping, N- and C-terminal amino acids and carbohydrate components of LPL purified from different tissues will be carried out. We plan to isolate and characterize rat VLDL subpopulations, study their distribution under a variety of metabolic conditions, and determine the results of LPL action on each VLDL subpopulation. Agents causing release of LPL from isolated adipocytes will be studied. These agents include a factor in serum which releases lipoprotein lipase from isolated adipocytes in vitro, a number of hormones, and serum lipoproteins or apolipoproteins. Since the capillary endothelium is viewed as the physiological site of LPL action, the role of cultured endothelial cells in binding and/or synthesis of the enzyme will be studied. Using antibody against LPL we will explore the mechanism involved in alterations of LPL activity in heart and adipose tissue.